Re: [PATCH] virtio/ringtest: fix up need_event math

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 26, 2017 at 10:36:47AM +0200, Cornelia Huck wrote:
> On Thu, 26 Oct 2017 04:48:01 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > last kicked event index must be updated unconditionally:
> > even if we don't need to kick, we do not want to re-check
> > the same entry for events.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  tools/virtio/ringtest/ring.c | 24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> Acked-by: Cornelia Huck <cohuck@redhat.com>

Actually it seems to sometimes trigger stalls when host and guest
are on the same physical core. To trigger:

./ring --sleep --host-affinity 0 --guest-affinity 0

This worries me since it's similar to what vhost does.

Still debugging - anyone see anything suspicious?


> I think virtio_ring_0_9 has the same issue?

I think it does, posted a patch.

-- 
MST